• Growing global population and climate change threaten food security
  • there is limited land to grow more groups

• C3 crops (e.g., rice, wheat, soybean) are limited by photorespiration, inefficient carbon fixation, and inefficient water use
  • all made worse under climate change factors (heat and drought)

• Rubisco, the key enzyme, can bind O₂ instead of CO₂, especially under heat and drought
  • leads to photorespiration – a wasteful process that reduces yield
  • forces stomata to be open more = more water loss
  • reduces carbon fixation

• Any improvement = huge gains in crop yield

• 5% reduction in photorespiration =
  • extra 68 million bushels of soybean
  • extra 23 million bushels of wheat
    
  • $540 million value (Walker et al. 2016)

• C3 crops can lose 10-40% of yield due to water related stress
  • water is transpired at a rate of hundreds of molecules per one CO₂ fixed

1-Photorespiration produces a toxic byproduct called glycolate, which wastes energy to detoxify
Engineeer new metabolic pathways (from bacteria or algae) into the plant’s chloroplasts to quickly recycle glycolate into useful products

2-Rubisco has a higher affinity for O₂ than CO₂ and is also slow
Modify Rubisco’s structure or assemble Rubisco from cyanobacteria or algae that have better kinetic properties

3-The dilemma of stomatal behavior limits photosynthesis
Introduce PEPC and nocturnal CO₂ fixation pathways (via CAM pathway)

4-The messy structure of C3 leaf anatomy is inefficient in supplying light and CO₂
Alter regulatory genes for mesophyll density, vein spacing, intercellular air space, or stomatal distribution
Alter regulatory genes that control Kranz anatomy (C4) and express C4 enzymes in the right cell types

Understanding photosynthetic anatomy and genetics is key to the next breakthroughs.